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Fragile X Syndrome
Fragile X: *'Consists of a family of genetic conditions that can impact both individuals and families in different ways.' *'There are three main classifications of Fragile X:' #Fragile X Syndrome (FXS): This disease is also referred to as Martin-Bell Syndrome. The syndrome results in a spectrum of characteristic physical, emotional, and mental limitations. Intellectual limitations can range from severe to mild. Fragile X Syndrome is the most common cause of inherited mental impairment. It is also the most common known cause of autism. #Fragile X-Associated Tremor/Ataxia Syndrome (FXTAS): This condition is seen later on in life for males. It affects balance, tremor, and memory. #Fragile X-Associated Primary Ovarian Insufficiency (FXPOI): In female carriers, problems with ovarian function can lead to infertility and early me nopause. *'The disorder was first identified by a geneticist Herbert Lubs in 1969.' *'Causes:' #Fragile X is caused by a change in the FMR-1 gene. #Normally, this gene makes a protein needed for your brain to grow properly. A defect in this gene makes your body produce too little of the protein, or none at all. *'Method of Inheritance:' #Fragile X Syndrome is a sex-linked gene, specifically X-linked, meaning that the gene gets inherited on the X chromosome. #For this reason, men are more likely to inherit the genes than women because they only inherit one X chromosome, while women inherit two. The gene on the X-chromosome is recessive, so women require two X chromosomes carrying Fragile X to show the full symptoms. Carrier women, those with only one X chromosome with the disease, may show some mild symptoms. #A premutation is a sequence of repeating CGG triplets. When the triplets exceed 200 in number, the person is then fully mutated for fragile X. *'Symptoms:' #Hand biting #Poor eye contact #Cluttered or repetitive speech, or a complete lack of speech #Attention problems #Hyperactivity #Emotional instability *'Typical physical phenotypes shown by those affected:' #Predominant ears (one or both) #Long face (vertical maxillary excess) #High-arched palate (related to the above) #Hyperextensible finger joints #Double-jointed thumbs #Flat feet #Soft skin #Larger testes in men (macroorchidism) #Low muscle tone *'Frequency:' #Fragile X Syndrome occurs in both sexes and all races and ethnicities. #Approximately 1 in every 16,000 people in the United States are diagnosed with Fragile X. #Approximately 1 in 3,600 to 4,000 males in the world are born with the full mutation for Fragile X. #Approximately 1 in 4,000 to 6,000 females in the world are born with the full mutation for Fragile X. #Approximately 1 in 800 men in the world are carriers of the Fragile X premutation. #Approximately 1 in 260 women in the world are carriers of the Fragile X premutation. *'Testing for Fragile X:' #Until 1991, the only laboratory test for Fragile X was a chromosome. #In 1991, a DNA test, the FMR-1 gene test, was introduced. This is the most accurate test (99+%) for detecting Fragile X. #A genetic test called polymerase chain reaction (PCR) is used to diagnose the disease. This test looks for a mutation in the FMR-1 gene. *'Prognosis:' #Early diagnosis and intensive intervention are the best prevention against severe cases of Fragile X syndrome. #However, adults diagnosed with the disease may benefit from vocational training and may be better off living in a supervised setting. #Prenatal Testing: If a pregnant woman wishes to identify any genetic risk factors, a detailed history of the family should be checked. Histories of retardation, autism, and other disorders may help identify risks for Fragile X syndrome. *'Standard treatment includes:' #Special education #Speech, occupational, and sensory integration training #Behavior modification programs #Surgical correction of heart defects is sometimes necessary. #Genetic counseling will benefit families of affected persons. #Folic acid has been found to improve hyperactivity and attention deficits in some pre-adolescent males.